The crystalline water that falls out of a cold atmosphere is snow.

Here's why:

* Crystalline structure: Snowflakes are hexagonal crystals of ice, formed when water vapor freezes in the atmosphere. This unique, symmetrical shape is a result of the water molecules arranging themselves in a specific lattice structure as they solidify.

* Cold atmosphere: For snow to form, the atmospheric temperature needs to be below freezing (0°C or 32°F). This is because water vapor must freeze to form ice crystals.

* Precipitation: Once the ice crystals grow large enough, they fall out of the atmosphere as snow.

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